S = input().strip()
N = len(S)
flag = True
for i in range(N):
    if S[i]!=S[N-1-i]:
        flag = False
        break
if not flag:
    print(N)
else:
    if N<=3:
        print(-1)
    else:
        n = S.count(S[0])
        if n==N and N%2==0:
            print(0)
        elif n==N and N%2==1:
            print(-1)
        else:
            print(N-2)